Many vessels in animals transport fluids from one bodily location to another. In some vessels, such as mammalian veins, natural valves are positioned along the length of the vessel to permit fluid flow in a substantially unidirectional manner along the length of the vessel. While natural valves may function for an extended time, some may lose effectiveness, which can lead to physical manifestations and clinical indications. Natural venous valves are susceptible to becoming insufficient following damage to valve leaflets and resulting formation of thrombus or scar tissue, compromising the ability of the valve leaflets to close properly. Once natural venous valves are damaged, venous valve insufficiency can occur, which can lead to various clinical indications such as discomfort and ulcers in the legs and ankles.
Minimally invasive techniques and instruments for placement of intraluminal medical devices have been developed to treat and repair such undesirable conditions within bodily vessels, including treatment of venous valve insufficiency. For example, intraluminal medical devices can be deployed in a vessel at a point of treatment, the delivery device withdrawn from the vessel, and the medical device retained within the vessel to provide sustained improvement in vascular valve function.
For treatment of many conditions, it is desirable that implantable medical devices comprise remodelable material. Implanted remodelable material provides a matrix or support for the growth of new tissue thereon, and remodelable material is resorbed into the body in which the device is implanted. Common events during this remodeling process include: widespread neovascularization, proliferation of granulation mesenchymal cells, biodegradation/resorption of implanted remodelable material, and absence of immune rejection. By this process, autologous cells from the body can replace the remodelable portions of the medical device.
A variety of remodelable materials are available for use in implantable medical devices. Naturally derived or synthetic collagenous materials can be used to provide remodelable surfaces on implantable medical devices. Naturally derived or synthetic collagenous material, such as extracellular matrix material, are another category of remodelable materials that include, for instance, submucosa, renal capsule membrane, dura mater, pericardium, serosa, and peritoneum or basement membrane materials. One specific example of an extracellular matrix material is small intestine submucosa (SIS). When implanted, SIS can undergo remodeling and can induce the growth of endogenous tissues upon implantation into a host. SIS has been used successfully in vascular grafts, urinary bladder and hernia repair, replacement and repair of tendons and ligaments, and dermal grafts.
Once implanted, however, remodelable material is often subjected to dynamic fluid flow. Changes in the flow rate, flow direction or fluid pressure of intraluminal fluid across an implanted remodelable material has the potential to disrupt or slow the remodeling process. The intraluminal fluid flow can be characterized by parameters such as pressure, direction, composition and flow rate across the interface. Intraluminal fluid flow in a vascular environment is subject to regular modulations in pressure and fluid flow between diastole and systole pressures. The remodeling process itself may be linked to the flow of fluid across the remodelable surface. Recent investigations have shown that SIS-based remodeling of implanted medical devices can occur by recruitment of cells directly from intraluminal circulation. See Brountzos, et al, “Remodeling of suspended small intestinal submucosa venous valve: an experimental study in sheep to assess the host cells' origin,” J. Vasc. Interv. Radiol., 14(3), 349-356 (March 2003).
Remodelable material implanted within a fluid-containing body vessel forms an interface between the remodelable material and the fluid within the body vessel that is contacting the remodelable material. The interface is potentially sensitive to, or responsive to, the flow of intraluminal fluid across the interface.
It is desirable to have systems, methods and kits relating to the implantation of medical devices in a body vessel that regulate fluid flow in the body vessel as taught herein, for example to promote the remodeling of tissue at an interface.